In conjunction with packet- or cell-switched data transfer there is often a need to manage a data flow constituted by data frames which have a pre-determined mutual order. Typically, the data transfer has to be managed so that a receiving end is capable of reconstructing the pre-determined mutual order of the data frames also in cases where a mutual order of two or more of the data frames is changed during the transfer and/or one or more of the data frames are lost and thus have to be retransmitted. The data frames can be for example Internet Protocol “IP” packets, Ethernet frames, or some other independently forwarded data entities. The data frames are typically provided with order indicators arranged to indicate the pre-determined mutual order of the data frames. The order indicators can be for example sequence numbers. In a case where the temporal reception order of the data frames at the receiving end is not the same as the pre-determined mutual order, the receiving end reorders the data frames on the basis of the order indicators.
A traditional way to apply the above-described principle based on the order indicators is such that the transmitting end and the receiving end carry out a hand-shaking process for establishing a logical connection state between the transmitting and receiving ends. The logical connection state is used for handling for example situations where one or more of the data frames are lost and thus have to be retransmitted. After the logical connection state has become needless, the logical connection state can be tore down. Inconveniences related to this approach are the need for the hand-shaking process prior to the transfer of the data frames and a need for mutually synchronized state-machine structures at the transmitting and receiving ends for maintaining the logical connection state.